You need an Extract, Transform, and Load Wizard [ETL]. APEX doesn't have one of those.

Instead, you'll need to use the DIY method (Do It Yourself).

DIY Method

Here are the thing you need to do

Load the file(s) into APEX_APPLICATION_TEMPORARY_FILES

Parse the data ...

... Into a staging table

validate the data

process the data

Step 0

There is a lot of code to wright. Keep related things in a Package. Maintain the Package in a Code Repository.

Step 1

This is just a configuration of the File Browse Item type. You should be able to look up the information in The Fine Manual.

Step 2

External Tables

Normally, External Table [ET] would be recommended. But, you'll have to worry about serialization to the ET. I wrote a plugin to handle that, I just haven't converted it to an apex.world version. ( - Process Type Plugin - External Table Processor )

the Application Express Data Loading wizard is indeed limited to 46 columns. That is the case in APEX 5.0 and it continues to be the case today. So, this is not an option for you.

For the upcoming release of Application Express, we plan to introduce new Data Loading functionality (https://apex.oracle.com/en/learn/resources/sod/). This will also include a PL/SQL API to parse CSV and other data. That API will support up to 300 columns. Of course, that is not available today. Until APEX 19.1 is available, the only option is some custom PL/SQL code which does the parsing for you.

Some time ago I adopted Antons Excel2Collections plugin to use a custom table we created with the inspiring name of staging_200. It had 200 columns, which was what we needed. That required a little cut & pasting, and a doddle of patience.

It's never let me down and has no tight coupling to APEX version. I think maybe there was a slight tweak in 18.x for the apex temp file view name.